Part of the Historical Society of Dauphin County, located behind the John Harris-Simon Cameron Mansion, the library research room and archives has been growing in size for over 130 years and includes more than a million photographs that pertain to Dauphin County.

The archives is located on the third floor of the library, and houses nine, distinct primary resource collections. These include the Alice Marshall Women's History Collection (1546-1997), the Penn State Harrisburg College History Archives (1966-Present), the Center for Pennsylvania Culture Studies Collection, the Holocaust and Jewish Studies Collection, the Three Mile Island Collection, and the newly-acquired J. Randall Plummer Collection of Photography.

The Hershey Community Archives' mission is to preserve, organize, describe, make available and interpret documents which promote the study and understanding of Milton and Catherine Hershey, their vision and legacy.

The Pennsylvania State Archives collects, preserves and makes available for study the permanently-valuable public records of the Commonwealth, with particular attention given to the records of state government. The State Archives also collects papers of private citizens and organizations relevant to Pennsylvania history.